In a saucepan, combine sugar, Splenda, cornstarch, cocoa, and salt. Gradually add egg yolks and milk, stirring constantly over medium heat until bubbly and thick. Add butter and stir for approximately 2 minutes. Add vanilla. If making pie, place mixture in pie crust. Note* Use medium egg yolks and can substitute yolks with Egg Beaters to equal 2 and 1/2 eggs.